Police officers working an undercover narcotics investigation in and around the Davis Square area last Friday focused their attention on a suspicious individual who was later placed under arrest for trafficking in heroin.

The suspect, later identified as John McLean, 52, of Boston, was kept under surveillance and was observed moving on foot through the Davis Square, eventually stopping at the shopping plaza in Porter Square.

Officers reportedly observed McLean using his cell phone and they felt that he appeared to be waiting to meet with someone.

Eventually two other males approached McLean and the three men reportedly began walking towards Cambridge.

One of the two men who had met up with McLean, later identified as David Wallace, 52, of Malden, was observed making a hand-to-hand transaction with McLean.

Police officers then approached the men, identifying themselves as law enforcement officers, and advised them of their Miranda rights.

A search was conducted and a small plastic bag was reportedly found on Wallace’s person, which officers on the scene believed to contain heroin.